Circuits included in an integrated circuit transmit and receive digital signals including data. A circuit which receives a digital signal determines whether the digital signal is a logic high level or a logic low level by comparing a level of a reference voltage with a level of the digital signal by using an input buffer which includes a comparator configured with a differential amplifier.
The reference voltage is set to a middle value between a potential defining a logic high level and a potential defining a logic low level, and serves as an absolute voltage which discriminates the logic level of the inputted digital signal.
In general, a reference voltage generation circuit starts to operate after a power-up period has ended, and selects one level among a plurality of levels, which are generated by a voltage division through a plurality of resistors, as a level of a reference voltage.
The reference voltage generation circuit operating in the above-described manner continuously maintains an enabled state after the power-up period is ended. Hence, a large amount of current is consumed, and it takes a long time to raise the reference voltage to the selected level.